1. Field of the Invention
The present invention relates to an anomaly diagnosis system for a nuclear reactor core, which gives an anomaly detection signal to a control rod driving mechanism or the like upon the detection of an anomaly in the nuclear reactor core, such as an excessive temperature rise in the reactor core, to shut down the nuclear reactor.
2. Description of the Prior Art
When an anomalous condition occurs in the fuel system of a nuclear reactor, a control rod is inserted in the core for safety control such as emergency shut down.
Conventionally, the anomalous reaction of the fuel in a nuclear reactor is diagnosed by detecting the flow rate and temperature of the coolant by a flow meter and a thermometer provided near the outlet of the coolant within the reactor vessel and connected through a cable to an external diagnosis unit, and the neutron flux density of the fuel assembly by a neutron detector inserted in the gap of the fuel assembly and connected through a cable to the external diagnosis unit.
Such a conventional diagnosis system, however, has the following problems.
First, the detection and warning of an anomalous condition by the detector provided at the exit of the reactor vessel or in the gap of the fuel assemblies delays the implementation of safety countermeasures.
Secondly, it is impossible to easily change the detector provided near the coolant outlet of the reactor vessel or in the gap of the fuel assemblies.
Thirdly, it is difficult to extend a cable connecting the detector to the outside reactor vessel and the deterioration of the cable reduces the reliability of anomaly diagnosis.
Fourthly, when the detector is inserted in the gap of the fuel assemblies, the detected neutron flux density and the detected temperature of the fuel assembly are dependent on the position and condition of the fuel assembly and are liable to deviate from true values, and thereby the reliability of anomaly diagnosis is reduced.